Abstract
This paper presents the corresponding compressive strength of RPC with variable pressure combined with heating rate, heating duration, and starting time of heating. The treatments applied were 8 MPa static pressure on fresh RPC prims and heat curing at 240 °C in an oven. The compressive strength test was conducted at 7-d and 28-d. The images of RPC morphology were captured on the surface of a fractured specimen using Scanning Electron Microscopy in Secondary Electron detector mode to describe pore filing mechanism after treatments. The results show that a heating rate at 50 °C/hr resulted in the highest compressive strength about 40 % more than those at 10 or 100 °C/hr. A heating duration of 48 hours led to the maximum compressive strength. Heat curing applied 2 days after casting resulted in the maximum compressive. Heat curing had a signicant effect on the compresssive strength due to the acceleration of both reactions (hydration and pozzolanic) and the degree of transformation from tobermorite to xonotlite. It is concluded that the optimum condition of treatments is both pressure and heat curing at 2-day after casting with a rate of 50 °C/hr for 48 hours.
Highlights
Reactive powder concrete (RPC), categorized as a type of ultra-high performance concrete (UHPC) due to having compressive strength > 140 MPa, has a different composition to ordinary concrete
This study has verified the properties of RPC mixtures with reduced cement content
The effects of pressure and high temperature curing treatment on compressive strength and paste morphology have been investigated in three ways, i.e. heating rate, heating duration and heating start time
Summary
Reactive powder concrete (RPC), categorized as a type of ultra-high performance concrete (UHPC) due to having compressive strength > 140 MPa, has a different composition to ordinary concrete. RPC can be developed by controlling three main variables: composition, pressure during setting period, and post-set heat curing [1]. Composition can be improved through a microstructural engineering approach by using fine aggregate only (no coarse aggregate), reducing waterbinder ratio, lowering the CaO–SiO2 ratio through the introducing of silica-rich pozzolona [2, 3] and adding fibre reinforcement to increase ductility [4]. Pressure induces three main effects: reducing the entrapped air, removing the excess water, and eliminating the porosity caused by chemical shrinkage [1]. Heat curing induces the acceleration of the pozzolanic reaction between amorphous silica and calcium hydroxide as well as the silicate and aluminate hydration reaction, and the modification of hydrate microstructure [5, 6]
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